September 26, 2013

Life-Bearing Oxygen Appeared On Earth Three Billion Years Ago

New research from the University of Copenhagen and University of British Columbia (UBC) has revealed that oxygen appeared 700 million years earlier than we previously thought. The findings, published in the journal Nature, raises new questions about the evolution of early life.

The research team examined the chemical composition of three-billion-year-old soils from South Africa, which are the oldest soils on Earth. They found evidence for low concentrations of atmospheric oxygen. Previous studies have indicated that oxygen began to accumulate in the atmosphere only about 2.3 billion years ago during a dynamic period in Earth's history referred to as the Great Oxygenation Event.

"We've always known that oxygen production by photosynthesis led to the eventual oxygenation of the atmosphere and the evolution of aerobic life," says Sean Crowe, assistant professor in the Departments of Microbiology and Immunology, and Earth, Ocean and Atmospheric Sciences at UBC.

"This study now suggests that the process began very early in Earth's history, supporting a much greater antiquity for oxygen producing photosynthesis and aerobic life," says Crowe, who conducted the research while a post-doctoral fellow at Nordic Center for Earth Evolution at the University of Southern Denmark in partnership with the center's director Donald Canfield.

For at least hundreds of millions of years after the Earth formed, there was no oxygen in the atmosphere. Currently, the planet's atmosphere is 20 percent oxygen due to photosynthetic bacteria. Like trees and other plants, these bacteria consume carbon dioxide and releases oxygen. The advent of these bacteria laid the foundation for oxygen breathing organisms to evolve and inhabit the planet.

"These findings imply that it took a very long time for geological and biological processes to conspire and produce the oxygen rich atmosphere we now enjoy," says Lasse Døssing from the University of Copenhagen.

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Image Below: Some of the rocks that Crowe and his colleagues studied. Credit: Nic Beukes